1. Field of the Invention
The present invention relates to a plasma display panel which displays picture using gas discharge between glass substrates, and more particularly, to a structure of a discharge electrode for a plasma display panel.
2. Discussion of the Related Art
Generally, a plasma display panel has high definition of a cathode ray tube(CRT), and various sized screens, and a thin thickness such as a liquid crystal display device. In this respect, the plasma display panel has lately attracted considerable attention as the most practical next generation display of flat panel displays. Also, since the plasma display panel has a weight of ⅓ of a CRT having the same sized screen, a large sized panel of 40 inch to 60 inch can thinly be fabricated at a thickness of 10 cm or below.
The CRT and the liquid crystal display device are limited by their sizes when digital data and full motion are displayed at the same time. However, the plasma display panel does not have such a problem. Furthermore, the CRT may be affected by magnetic force but the plasma display panel is not susceptible to magnetic force, thereby providing stable image to viewers. Moreover, since each pixel of the plasma display panel is digitally controlled, image distortion of corners on a screen does not occur. Thus, the plasma display panel can provide higher picture quality than the CRT.
The plasma display panel displays picture using its internal gas discharge. Since active devices are not required for each cell, the fabrication process is simple. Also, a large sized screen and high response speed can be obtained. For these reasons, the plasma display panel is widely used as a picture display device having a large sized screen, particularly a picture display device for high definition televisions, monitors, and indoor and outdoor advertizement.
The plasma display panel includes two glass substrates coated with electrodes, and a gas sealed between the glass substrates. The electrodes formed in the glass substrates oppose each other in vertical direction, and pixels are formed in crossing portions of the electrodes. A voltage of 100V or more is applied across the electrodes to produce glow discharge within minute cells around the electrodes to emit light from each cell, thereby displaying picture information.
Such a plasma display panel is classified into three types, a two-electrode type, a three-electrode type, and a four-electrode type in accordance with the number of electrodes assigned to each cell. Of them, the two-electrode type is intended that an address voltage and a sustain voltage are applied to two electrodes. The three-electrode type is generally called an area discharge type and is intended that a discharge cell is switched or sustained by a voltage applied to an electrode disposed at a side of the discharge cell.
Such a related art plasma display panel of three-electrode area discharge type will be described with reference to the accompanying drawings.
FIG. 1 is an exploded perspective view of upper and lower substrates of a general plasma display panel, and FIG. 2 is a sectional view of a related art plasma display panel.
As shown in FIGS. 1 and 2, the plasma display panel of three-electrode area discharge type includes an upper substrate 10 and a lower substrate 20 which are bonded to each other with a certain space and sealed.
The upper substrate 10 includes scan electrodes 16 and 16xe2x80x2, sustain electrodes 17 and 17xe2x80x2, a dielectric layer 11, and a protection layer 12. The scan electrodes 16 and 16xe2x80x2 are formed in parallel to the sustain electrodes 17 and 17xe2x80x2. The dielectric layer 11 is deposited on the scan electrodes 16 and 16xe2x80x2 and the sustain electrodes 17 and 17xe2x80x2.
The lower substrate 20 includes an address electrode 22, a dielectric film 21 formed on an entire surface of the substrate including the address electrode 22, an isolation wall 23 formed on the dielectric film 21 between the address electrodes, and a phosphor 24 formed on surfaces of the isolation wall 23 in each discharge cell and of the dielectric film 21. The upper substrate and the lower substrate 20 are joined together by a frit glass. Inert gases such as He and Xe are mixed in a space between the upper substrate 10 and the lower substrate 20 at a pressure of 400 to 500 Torr. The space is used as a discharge area.
In general, a mixing gas of Hexe2x80x94Xe is filled in a discharge area of a DC type plasma display panel. A mixing gas of Nexe2x80x94Xe is filled in a discharge area of an AC type plasma display panel.
The scan electrodes 16 and 16xe2x80x2 and the sustain electrodes 17 and 17xe2x80x2 are of transparent electrodes and metals so as to increase optical transmitivity of each discharge cell, as shown in FIGS. 3 and 4. That is to say, the electrodes 16 and 17 are of transparent electrodes while the electrodes 16xe2x80x2 and 17xe2x80x2 are of metals.
A discharge voltage from an externally provided driving integrated circuit(IC) is applied to the metal scan and sustain electrodes 16xe2x80x2 and 17xe2x80x2. The discharge voltage applied to the metal electrodes 16xe2x80x2 and 17xe2x80x2 is applied to the transparent electrodes 16 and 17 to generate discharge between the adjacent transparent electrodes 16 and 17. The transparent electrodes 16 and 17 have an overall width of about 300 xcexcm and are made of indium oxide or tin oxide. The metal electrodes 16xe2x80x2 and 17xe2x80x2 are formed of a three-layered thin film of Crxe2x80x94Cuxe2x80x94Cr. At this time, the bus electrodes 16xe2x80x2 and 17xe2x80x2 have a line width of ⅓ of a line width of the transparent electrodes 16 and 17.
FIG. 5 is a wiring diagram of scan electrodes (Smxe2x88x921, Sm, Sm+1, . . . , Snxe2x88x921, Sn, Sn+1) and sustain electrodes (Cmxe2x88x921, Cm, Cm+1, . . . , Cnxe2x88x921, Cn, Cn+1) arranged on the upper substrate. In FIG. 5, the scan electrodes are insulated from one another while the sustain electrodes are connected in parallel. Particularly, a block indicated by a dotted line in FIG. 5 shows an active area where an image is displayed and the other blocks show inactive areas where an image is not displayed. The scan electrodes arranged in the inactive areas are generally called dummy electrodes 26. The number of the dummy electrodes 26 are not specially limited.
The operation of the aforementioned AC type plasma display panel of three-electrode area discharge type will be described with reference to FIGS. 6a to 6d. 
If a driving voltage is applied between the address electrodes and the scan electrodes, opposite discharge occurs between the address electrodes and the scan electrodes as shown in FIG. 6a. The inert gas injected into the discharge cell is instantaneously excited by the opposite discharge. If the inert gas is again transited to the ground state, ions are generated. The generated ions or some electrons of quasi-excited state come into collision with a surface of the protection layer as shown in FIG. 6b. The collision of the electrons secondarily discharges electrons from the surface of the protection layer. The secondarily discharged electrons come into collision with a plasma gas to diffuse the discharge. If the opposite discharge between the address electrodes and the scan electrodes ends, wall charges having opposite polarities occur on the surface of the protection layer on the respective address electrodes and the scan electrodes.
If the discharge voltages having opposite polarities are continuously applied to the scan electrodes and the sustain electrodes and at the same time the driving voltage applied to the address electrodes is cut off, area discharge occurs in a discharge area on the surfaces of the dielectric layer and the protection layer due to potential difference between the scan electrodes and the sustain electrodes as shown in FIG. 6d. The electrons in the discharge cell come into collision with the inert gas in the discharge cell due to the opposite discharge and the area discharge. As a result, the inert gas in the discharge cell is excited and ultraviolet rays having a wavelength of 147 nm occur in the discharge cell. The ultraviolet rays come into collision with the phosphors surrounding the address electrodes and the isolation wall so that the phosphors are excited. The excited phosphors generate visible light rays, and the visible light rays display an image on a screen.
However, the aforementioned related art plasma display panel has several problems.
Since the distance between the electrodes of the discharge area is short as compared with a general discharge tube display, ultraviolet rays in a positive column region having good emitting efficiency are not generated. In other words, as shown in FIG. 7, since discharge current (2) generated in the transparent electrodes 16 and 17 spaced apart from a field convergence area is remarkably lower than discharge current (1) generated in the transparent electrodes 16 and 17 of the field convergence area, discharge begins in the field convergence area and ends in the end of the transparent electrodes, thereby causing short discharge time. As a result, it is difficult to expand the discharge distance beyond the widths of the transparent electrodes 16 and 17. If the widths of the transparent electrodes 16 and 17 become wide to secure longer discharge distance, discharge capacitance increases proportionally, thereby increasing discharge current. This reduces emitting efficiency and increases power consumption.
Consequently, in the related art plasma display panel, since the discharge distance and the distance time are short, ultraviolet rays in a negative glow region occur but ultraviolet rays in a positive column region do not occur. For this reason, emission efficiency becomes poor, thereby causing poor picture quality.
Accordingly, the present invention is directed to a plasma display panel that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a plasma display panel in which the discharge distance is expanded to generate ultraviolet rays in a positive column region and discharge current is reduced to decrease power consumption.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the scheme particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a plasma display panel according to the present invention includes first and second outer electrodes formed at both sides of a substrate in a unit pixel region, and first and second inner electrodes formed between the first and second outer electrodes, wherein a first voltage is applied to the first outer electrode and the first inner electrode, and a second voltage is applied to the second outer electrode and the second inner electrode.
In another aspect, a plasma display panel according to the present invention includes a plurality of first outer electrodes successively formed on a substrate at predetermined intervals, a plurality of first inner electrodes formed in parallel to the first outer electrodes and mated with the first outer electrodes one by one, a plurality of second outer electrodes formed in parallel to the first outer electrodes, and a plurality of second inner electrodes formed between the first inner electrodes and the second outer electrodes and mated with the second outer electrodes one by one.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.